( Ivan Vin DataApex Ltd. Praha ...)Practical Aspects of Evaluation of Chromatographic Data in Size Exclusion Chromatography

Introduction
Determination of MW distribution of polymers by the liquid chromatographic methods with concentration or mass selective detectors is a simple, affordable solution for process quality control or research and development of synthetic and natural polymers. Absolute methods with molecular weight and viscosity detectors are more demanding and not always affordable.

Using this methods, precision and accuracy of calculated values is of prime importance. GPC/SEC is presently the most common method for determination of molar masses and molar mass distributions of synthetic polymers. It is known for its high intra-laboratory repeatability (precision) of the molar mass data, often better than +/- 5%. At the same time, GPC suffers from a rather low inter-laboratory reproducibility (accuracy). The molar mass data scatter is +/- 10-20% at best and often may reach even several hundreds of percent. In this note, we will discuss the potential sources of errors during GPC data.

The factors influencing the GPC data, like column quality (resolution, efficiency), sample preparation, sample concentration and volume, extracolumn dispersion, sample/solvent/column interactions, detector sensitivity and linearity, instrument flow rate and temperature stability are outside scope of this note and are widely discussed elsewhere.

Factors influencing data processing in GPC/SEC
The data processing in chromatography software consists of data acquisition, integration, calibration and calculation of the results. The possible problems in those areas will be discussed.

Data Acquisition
Analog signal
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